Model Predictive Control based Coordinated Control for Free-Flying Space Manipulator Systems

Kurzfassung

Space Manipulator Systems (SMS) used in On-Orbit Servicing (OOS) missions are over-actuated, and safety critical systems that perform complex tasks in space. We propose a coordinated control for a free-flying SMS, which is based on a cascaded output tracking nonlinear model predictive control, to simultaneously control the spacecraft-base and manipulator of the SMS. The output tracks a given end-effector pose trajectory, and by using an artificial reference the controller stays feasible even for an unreachable trajectory. Moreover, the systems over-actuation is optimally resolved, such that the base of the SMS can be utilized to generate an unrestricted workspace for robotic operations. Throughout the entire mission, critical constraints related to system and safety, including collision avoidance, field of view of sensor devices, joint limitations, and actuator saturations, are integrated as hard constraints. Simulations of the most challenging mission phases, such as the approach and detumbling of a target spacecraft, as well as an escape maneuver verify the performance, reliability, and flexibility of our coordinated control concept.